Inventors have proposed various lighting devices composed of an LED (light emitting) module in which light emitting units are formed on a front surface of a substrate, a heatsink, and a socket for mounting the LED module to the heatsink (for example, see Japanese Laid-Open Patent Application No. 2004-265626 and Japanese Laid-Open Patent Application No. 2004-265619).
The substrate of an LED module is composed of an insulating plate and a metal plate (heat conducting plate) layered together, and the light emitting unit is composed of a plurality of LEDs that are mounted in a central area of the front surface of the insulating plate. The metal plate ensures stiffness of the LED module as well as having a function of conducting heat generated when the light emitting unit (in other words, the LEDS) emits light to the heatsink.
The socket is mounted on a flat surface of the heatsink from over the LED module so as to cover the front side thereof. In this mounted state, pressing units of the socket press against edge parts of the insulating plate, thus having a function of pressing the LED module, in other words the metal plate, against the heat sink.